Brushless motor and fluid pump having the same

ABSTRACT

A fuel pump includes a stator core that has teeth being circumferentially arranged. Coils are formed by concentrically winding a wire around each of the teeth. The coils circumferentially generate magnetic poles in inner circumferential peripheries of the teeth when being supplied with electricity. The magnetic poles being switched by controlling electricity supplied to the plurality of coils. A rotator has an outer circumferential periphery opposed to the inner circumferential peripheries. The outer circumferential periphery defines magnetic poles different from each other with respect to a rotative direction thereof. A pump portion that has a rotor member rotated by the rotator for pumping fuel. An electrically insulative resin material is charged between the teeth, which are circumferentially adjacent to each other, thereby being molded such that the electrically insulative resin material covers the plurality of coils.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-302698 filed on Oct. 18, 2005.

FIELD OF THE INVENTION

The present invention relates to a brushless motor and a fuel pump having the brushless motor.

BACKGROUND OF THE INVENTION

For example, according to JP-A-5-340345, a fuel pump includes a brushless motor as a driving source. In general, a motor (brush motor) having a brush causes a loss such as slide resistance between a commutator and a brush, electric resistance between the commutator and the brush, and fluid resistance caused in grooves, via which the commutator is divided into segments. By contrast, a brushless motor may not cause the above losses arising the brush motor. Therefore, a brushless motor is higher than a brush motor in motor efficiency, so that a fuel pump having a brushless motor is enhanced in pump efficiency. Here, the pump efficiency is a ratio of an amount of work produced by the fuel pump relative to electricity supplied to the fuel pump. The amount of work produced by the fuel pump can be calculated by multiplying fuel discharge pressure by a fuel discharge amount.

When the amount of work is constant, as the efficiency of the fuel pump increases, a motor portion can be downsized, so that the fuel pump can be downsized. A fuel pump including a brushless motor may be applied to a small vehicle such as a motor cycle.

A fuel pump may be downsized by reducing a space occupied by coils. In addition, a coil in a fuel pump needs to be protected from corrosion due to exposure to fuel such as debased fuel or low quality fuel is used.

The JP-A-5-340345 does not disclose reduction of the space occupied by the coils in the brushless motor applied to the fuel pump. In addition, in JP-A-5-340345, a case is provided for accommodating the stator, which includes the coils and the stator core, for protecting the stator from corrosion. The components constructing the case are welded for tightly sealing. Accordingly, in this structure manufacturing work is necessary for welding the case.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, it is an object of the present invention to produce a brushless motor that includes coils, which can be protected by a simple structure. It is another object of the present invention to produce a fuel pump having the brushless motor.

According to one aspect of the present invention, a fluid pump includes a stator core that includes a plurality of teeth, which is circumferentially arranged. The fluid pump further includes a plurality of coils each being formed by concentrically winding a wire around an outer circumferential periphery of each of the plurality of teeth. The plurality of coils circumferentially generates magnetic poles in inner circumferential peripheries of the plurality of teeth when being supplied with electricity. The magnetic poles are switched by controlling electricity supplied to the plurality of coils. The fluid pump further includes a rotator that is rotatable around the inner circumferential peripheries of the plurality of teeth, the rotator having an outer circumferential periphery opposed to the inner circumferential peripheries of the plurality of teeth. The outer circumferential periphery defines magnetic poles different from each other with respect to a rotative direction of the rotator. The fluid pump further includes a pump portion that has a rotor member, the rotator rotating the rotor member for pumping fluid. The fluid pump further includes an electrically insulative resin material that is charged between the plurality of teeth, which are circumferentially adjacent to each other. The electrically insulative resin material is molded such that the electrically insulative resin material covers the plurality of coils.

According to another aspect of the present invention, a brushless motor is at least partially submerged in fluid. The brushless motor includes a stator core that includes a plurality of teeth, which is circumferentially arranged. The brushless motor further includes a plurality of coils each being formed by concentrically winding a wire around an outer circumferential periphery of each of the plurality of teeth. The plurality of coils circumferentially generates magnetic poles in inner circumferential peripheries of the plurality of teeth when being supplied with electricity, the magnetic poles being switched by controlling electricity supplied to the plurality of coils. The brushless motor further includes a rotator that is rotatable around the inner circumferential peripheries of the plurality of teeth, the rotator having an outer circumferential periphery opposed to the inner circumferential peripheries of the plurality of teeth. The outer circumferential periphery defines magnetic poles different from each other with respect to a rotative direction of the rotator. The brushless motor further includes an electrically insulative resin material that is charged between the plurality of teeth, which are circumferentially adjacent to each other. The electrically insulative resin material is molded such that the electrically insulative resin material covers the plurality of coils. The electrically insulative resin material substantially insulates the plurality of coils from the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a longitudinal partially sectional view showing a fuel pump according to a first embodiment;

FIG. 2 is a sectional view taken along the line II-II in FIG. 1;

FIG. 3 is a perspective view showing a slant restricting member of the fuel pump;

FIG. 4 is a sectional view showing a fuel pump according to a second embodiment; and

FIG. 5 is a sectional view showing a fuel pump according to a third embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

As shown in FIG. 1, a fuel pump 10 of this embodiment is an in-tank turbine pump that is provided in a fuel tank of a motorcycle with an engine size of 150 cc, for example.

The fuel pump 10 includes a pump portion 12 and a motor portion 13. The motor portion 13 rotates the pump portion 12. The housing 14 accommodates both the pump portion 12 and the motor portion 13. A pump case 20 and an end cover 48 are fixed by crimping both axial ends of the housing 14. The thickness of a portion of the housing 14 covering the outer circumferential periphery of the stator core 30 in the motor portion 13 is less than the thickness of a portion defining a step 15 in the pump portion 12. The housing 14 is not necessary for defining a magnetic circuit. Therefore, the outer diameter of the motor portion 13 can be reduced by reducing the thickness of the housing 14 surrounding the outer circumferential periphery of the stator core 30.

The pump portion 12 is a turbine pump that includes pump cases 20, 22, and an impeller 24. The pump case 22 is abutted axially onto the step 15 of the housing 14. Thus, the pump case 22 is axially aligned. The pump case 20 is fixed by crimping one end of the housing 14. Axial force is caused by the crimping, thereby producing pressure for axially pressing the pump case 22 and the pump case 20 respectively onto the step 15 and the pump case 22, so that fuel is sealed.

The pump cases 20, 22 rotatably accommodate the impeller 24 as a rotor member. The pump cases 20, 22 and the impeller 24 define pump passages 202 in C-shapes thereamong. Fuel is drawn through an inlet port 200 provided to the pump case 20, and is pressurized through the pump passages 202 by rotation of the impeller 24, thereby being press-fed toward the motor portion 13. The fuel press-fed toward the motor portion 13 is supplied toward an engine through an outlet port 206 after passing through a fuel passage 204 defined between the stator core 30 and a rotator 60.

As referred to FIGS. 1, 2, the motor portion 13 is a brushless motor that includes the stator core 30, bobbins 40, coils 42, and the rotator 60. The stator core 30 is constructed of six cores 32 that are circumferentially arranged. An unillustrated control apparatus controls current supplied to the coils 42 in accordance with a rotational position of the rotator 60, thereby switching magnetic poles defined in the inner circumferential peripheries of the cores 32. The inner circumferential peripheries of the cores 32 are opposed to the rotator 60.

As referred to FIG. 2, each of the cores 32 has a tooth 33 and an outer circumferential periphery 34. Each core 32 is integrally formed by crimping magnetic steel plates, which are stacked with respect to the axial direction of the core 32. The tooth 33 protrudes from the center of the outer circumferential periphery 34 inwardly toward the rotator 60. Each of the bobbins 40 formed of electrically insulative resin engages with each of the cores 32. Six of the outer circumferential peripheries 34 define a toroidal core. Each of the outer circumferential peripheries 34 is in a substantially arc shape that has a circumferentially regular width.

Each of the coils 42 is constructed by concentrically winding a wire around the outer periphery of the bobbin 40 of each of the cores 32 in a condition where each of the six cores 32 is a single component before being circumferentially arranged to be the stator core 30. Each of the coils 42 electrically connects with each of terminals 44 on the side of the end cover 48 in a condition depicted by FIG. 1.

An electrically insulative resin material 46 is charged between the teeth 33, which are circumferentially adjacent to each other, thereby being molded such that the electrically insulative resin material 46 covers the coils 42. The electrically insulative resin material 46 is integrally molded with the end cover 48 that covers the end of the stator core 30 on the opposite side of the pump portion 12 with respect to the stator core 30. The electrically insulative resin material 46 is integrally formed with the end cover 48, so that components constructing the fuel pump 10 can be reduced, and manufacturing work for assembling the fuel pump 10 can be reduced.

As shown in FIG. 3, the slant restricting member 50 has a through hole in the center thereof. The slant restricting member 50 has claws 52 and fitting holes 54. The claws 52 hook to the bobbins 40. Each of the terminals 44 fits to each of the fitting holes 54. FIG. 3 depicts a substantially annular slant restricting member 50 before the electrically insulative resin material 46 is molded. Each of the terminals 44 fits to each of the fitting holes 54 of the slant restricting member 50, so that the terminals 44 can be restricted from being inclined and causing interference with peripheral components when the electrically insulative resin material 46 is molded of resin.

As referred to FIGS. 1, 2, the rotator 60 includes a shaft 62 and a permanent magnet 64. The rotator 60 is rotatable around the inner circumferential periphery of the stator core 30. The permanent magnet 64 is directly fitted to the outer circumferential periphery of the shaft 62. The outer circumferential periphery of the shaft 62 may be knurled. The shaft 62 is rotatably supported by bearings 26 at both ends. The permanent magnet 64 may be a resin magnet that is produced by mixing magnetic powder with thermoplastic resin such as polyphenylene sulfide (PPS). The permanent magnet 64 is shaped to be substantially cylindrical. The permanent magnet 64 has eight magnetic poles 65 arranged with respect to the rotative direction of the rotator 60. The eight magnetic poles 65 are magnetized toward the outer circumferential periphery of the permanent magnet 64. The outer circumferential periphery of the permanent magnet 64 is opposed to the stator core 30. The magnetic poles are different from each other with respect to the rotative direction of the rotator 60.

The end cover 48 has the outlet port 206 that accommodates a valve member 70, a stopper 72, and a spring 74 that construct a check valve. Thus, the end cover 48 also serves as a housing of the check valve, so that components constructing the fuel pump 10 can be reduced, and manufacturing work for assembling the fuel pump 10 can be also reduced.

The valve member 70 is lifted against bias force of the spring 74 when pressure of fuel pressurized in the pump portion 12 becomes equal to or greater than predetermined pressure, so that fuel is discharged toward the engine through the outlet port 206. The valve member 70 restricts fuel, which is discharged from the fuel pump 10, from causing reverse flow.

In the first embodiment, each of the coils 42 is constructed of the concentrated winding formed around the tooth 33 of each of the cores 32, so that an occupancy rate of the winding is enhanced compared with a structure of distributed winding, for example. This occupancy rate of the winding is a rate of a winding area of the winding with respect to a winding space, in which the winding is located. Therefore, a winding space occupied by each of the coils 42 is reduced by increasing the occupancy rate when the number of the winding is constant. Consequently, the motor portion 13 can be reduced, so that the fuel pump 10 can be reduced.

Furthermore, the electrically insulative resin material 46 is charged between the teeth 33, which are circumferentially adjacent to each other, thereby being molded such that the electrically insulative resin material 46 covers the coils 42. Therefore, the coils 42 are protected from corrosion due to exposure to fuel, and the coils 42 can be restricted from being exposed to foreign matters by applying a simple structure. Furthermore, the electrically insulative resin material 46 is capable of protecting the coils 42, which is constructed of the concentrated winding, from causing deformation in the winding.

Furthermore, the teeth 33 of the stator core 30 are separate from each other. Therefore, the wire can be concentrically wound around each of the teeth 33 in a condition where each of the teeth 33 is a single component before being circumferentially arranged to be the stator core 30. Thus, the manufacturing work for concentrically winding the wire around each of the teeth 33 can be facilitated.

Second and Third Embodiments

As shown in FIG. 4, in the second embodiment, a fuel pump 80 includes a stator core 82 that is constructed of a toroidal core 84 and six teeth 85. The six teeth 85 are circumferentially arranged around the inner circumferential periphery of the toroidal core 84. The toroidal core 84 and the teeth 85 are separate components. The teeth 85 are also separate components. The electrically insulative resin material 46 is charged between the teeth 85, which are circumferentially adjacent to each other, thereby being molded such that the electrically insulative resin material 46 covers the coils 42.

As shown in FIG. 5, in the third embodiment, a fuel pump 90 includes a stator core 92 that is constructed of a toroidal core 94 and six teeth 95. The six teeth 95 are circumferentially arranged. The six teeth 95 engage with the inner circumferential periphery of the toroidal core 94. The toroidal core 94 and the teeth 95 are separate components. The teeth 95 are also separate components. The electrically insulative resin material 46 is charged between the teeth 95, which are circumferentially adjacent to each other, thereby being molded such that the electrically insulative resin material 46 covers the coils 42.

In the second and third embodiments, the concentrated winding can be readily formed by concentrically winding the wire around the tooth 85, 95 to construct each of the coils 42 in a condition where each of the teeth 85, 95 is a single component before being assembled to be the stator core 82, 92.

Furthermore, in the third embodiment, each of the coils 42 is wound around each of the teeth 95, and the teeth 95 engage with the toroidal core 94. Therefore, the teeth 95 can be readily aligned with respect to the circumferential direction.

In the above embodiments, the brushless motor may be at least partially submerged in fluid such as fuel. The electrically insulative resin material 46 is molded such that the electrically insulative resin material 46 at least partially covers the plurality of coils 42, so that the electrically insulative resin material 46 substantially insulates the coils 42 from the fluid. Thus, the coils 42 can be protected from being exposed to the fluid.

Other Embodiment

In the above embodiments, the teeth, which are circumferentially arranged to construct the stator core, are separate components. Alternatively, the teeth may be integrally formed such that the teeth are circumferentially arranged.

In the above embodiments, the pump portion 12 is constructed of the turbine pump including the impeller 24. Alternatively, the pump portion may be constructed of a pump having another structure such as a gear pump.

The above structures of the embodiments can be combined as appropriate.

In the above embodiments, the structures of the brushless motor is applied to the fuel pump. However, the above structures are not limited to the application of the fuel pumps. The above structures can be applied to any other fluid pumps.

Various modifications and alternations may be diversely made to the above embodiments without departing from the spirit of the present invention. 

1. A fluid pump comprising: a stator core that includes a plurality of teeth, which is circumferentially arranged; a plurality of coils each being formed by concentrically winding a wire around an outer circumferential periphery of each of the plurality of teeth, the plurality of coils circumferentially generating magnetic poles in inner circumferential peripheries of the plurality of teeth when being supplied with electricity, the magnetic poles being switched by controlling electricity supplied to the plurality of coils; a rotator that is rotatable around the inner circumferential peripheries of the plurality of teeth, the rotator having an outer circumferential periphery opposed to the inner circumferential peripheries of the plurality of teeth, the outer circumferential periphery defining magnetic poles different from each other with respect to a rotative direction of the rotator; a pump portion that has a rotor member, the rotator rotating the rotor member for pumping fluid; and an electrically insulative resin material that is charged between the plurality of teeth, which are circumferentially adjacent to each other, wherein the electrically insulative resin material is molded such that the electrically insulative resin material covers the plurality of coils.
 2. The fluid pump according to claim 1, wherein the plurality of teeth is separate from each other.
 3. The fluid pump according to claim 1, wherein the electrically insulative resin material is integrally molded with a cover that covers an end of the stator core on an opposite side of the pump portion with respect to the stator core.
 4. The fluid pump according to claim 3, further comprising: a valve member that restricts fluid, which is pumped using the pump portion, from causing reverse flow; and a stopper that restricts a lift position of the valve member, wherein the cover accommodates the valve member and the stopper.
 5. The fluid pump according to claim 1, further comprising: a plurality of terminals that is insert-molded in the electrically insulative resin material, the plurality of terminals electrically connecting with the plurality of coils; and a slant restricting member that restricts the plurality of terminals from being slanted when the electrically insulative resin material is molded.
 6. The fluid pump according to claim 1, wherein the stator core includes a toroidal core that circumferentially surrounds outer circumferential peripheries of the plurality of teeth, and each of the plurality of teeth engages with the toroidal core.
 7. A brushless motor that is at least partially submerged in fluid, the brushless motor comprising: a stator core that includes a plurality of teeth, which is circumferentially arranged; a plurality of coils each being formed by concentrically winding a wire around an outer circumferential periphery of each of the plurality of teeth, the plurality of coils circumferentially generating magnetic poles in inner circumferential peripheries of the plurality of teeth when being supplied with electricity, the magnetic poles being switched by controlling electricity supplied to the plurality of coils; a rotator that is rotatable around the inner circumferential peripheries of the plurality of teeth, the rotator having an outer circumferential periphery opposed to the inner circumferential peripheries of the plurality of teeth, the outer circumferential periphery defining magnetic poles different from each other with respect to a rotative direction of the rotator; and an electrically insulative resin material that is charged between the plurality of teeth, which are circumferentially adjacent to each other, wherein the electrically insulative resin material is molded such that the electrically insulative resin material covers the plurality of coils, and the electrically insulative resin material insulates the plurality of coils from the fluid. 